We shall continue the following studies: 1. The mechanism of silicate transport in diatoms in particular the purification and characterization of a silicate ionophore we have isolated from Nitzschia alba, and determine its role. 2. The role of silicate in the synthesis of the nuclear DNA polymerase of Cylindrotheca fusiformis, to determine the program of mRNA synthesis during the cell cycle and silicate starvation. 3. The effect of silicate on the synthesis and regulation of phosphodiesterases, adenylate cyclase and guanylate cyclase in C. fusiformis. 4. The morphology and morphogenesis of the silica spheres in diatoms cell wall.